Spring cushion and release mechanism for ground-working tool



1966 G. MANNHEIM ETAL 3,

SPRING CUSHION AND RELEASE MECHANISM FOR GROUND-WORKING TOOL 2 Sheets-Sheet 1 Filed Aug. 15, 1962 Dec. 20, 1966 cs. MANNHEIM ETAL 3,292,713

SPRING CUSHION AND RELEASE MECHANISM FOR GROUND-WORKING TOOL Filed Aug. 15, 1962 2 Sheets-Sheet 2 United States Patent 3,292,713 SPRING CUSHION AND RELEASE MECHANISM FOR GROUND-WORKING TOOL Guenther Mannheim, South Bend, Earl D. Zeltwanger, Mishawaka, and Donald E. Kuska, South Bend, Ind., assignors to Oliver Corporation, Chicago, 111., a corporation of Delaware Filed Aug. 15, 1962, Ser. No. 217,216 8 Claims. (Cl. 172-269) The present invention relates to agricultural implements and, more particularly, to an automatic spring cushion and release mechanism for a ground-working tool, such as a plow, whereby to permit first a rearward shifting or sliding movement, and then, if the forces become great enough, a rearward and upward swinging movement of such a tool, when same comes into engagement with an unyielding obstruction.

An important object of the present invention is to provide a new and improved agricultural implement having a novel spring cushion action and release mechanism whereby when the ground-working tool thereof engages an obstruction, such as stones, boulders, stumps, roots, etc., the impact on the tool will be cushioned and, if a predetermined overload occurs, the tool will be automatically released for rearward and upward pivoting movement to clear the obstruction and prevent damage to the tool.

Another important object of the present invention is to provide a new and improved implement of the character described wherein the pivot connection of the groundworking tool to the supporting structure therefor is spaced well above the tool itself so that the arc through which the tool swings when released is relatively flat and shallow.

Another important object of the present invention is to provide a new and improved implement of the character described wherein the ground-working tool when it engages an obstruction is first longitudinally shifted rearwardly relative to its supporting structure whereby to reduce the impact forces thereon, and wherein, the trip or release portion of the mechanism becomes operable thereafter only if the overload exceeds a predetermined value sufficient to shift the tool to its rearwardmost position relative to its supporting structure.

A further object of the present invention is to provide a new and improved implement of the character described wherein the release portion of themechanism may be manually actuated to swing the tool upwardly to position it more conveniently for replacement of plow points, cutting edges, teeth, etc.

A further object of the invention is to provide a new and improved implement of the character described wherein the moving parts of the trip or release mechanism are mounted on and carried with the tool.

A more detailed object of the present invention is to provide a new and improved implement of the character described including a tool-carrying frame which is mounted on a traveling support beam for both pivoting movement relative thereto and longitudinal movement forwardly and rearwardly thereof, means normally interlocking the tool-carrying frame to the support beam to prevent relative pivoting movement therebetween when the tool-carrying frame is disposed forwardly of its rearwardmost position relative to the support beam, and yieldable means resiliently urging the tool-carrying frame into its forwardmost position relative to the support beam, the interlocking means being automatically releasable to permit rearward and upward pivoting movement of the tool-carrying frame when same is longitudinally shifted substantially into its rearwardmost position relative to 3,292,713 Patented Dec. 20, 1966 "ice the support beam, as upon engagement of the tool with an unyielding obstruction.

Another important object of the present invention is to provide a new and improved implement of the character described wherein the mounting and spring release means for the tool-carrying frame includes a forward roller which is movable generally forwardly and rearwardly of the support beam in an elongated slot and about which the tool-carrying frame is pivotable and a rear roller which is engageable in a rearwardly opening slot of substantial depth formed in the support beam to interlock the tool-carrying frame against pivoting movement relative to the support beam.

Still another important object is the provision of an implement of the character described wherein there is a mounting beam extending in a fore and aft direction with the rear portion being generally in the form of a vertical plate having substantial depth and the support for a ground-working element is mounted on the lower end of a frame the upper portion of which frame is in the form of a pair of gusset plates fitting in rotatable sliding and bearing engagement on opposite sides of said vertical plate so as to receive support therefrom against twisting or rocking movement.

Certain other objects of the invention will, in part, be obvious, and will in part appear hereinafter.

For a more complete understanding of the nature and scope of the invention reference may now be had to the accompanying drawings wherein:

FIG. 1 is a side elevational view of a plow element embodying the invention with the working position of the plow bottom being shown in full line and with the fully released position of the plow bottom and the relatively flat shallow arc of the plow point as it is pivoted upwardly and rearwardly from its working position into its fully released position being shown in broken lines;

FIG. 2 is an enlarged scale top plan view of the plow element of FIG. 1 when in its working position with the plow bottom removed;

FIG. 3 is an enlarged scale rear end view of the plow element of FIG. 1 when in its working position with the plow bottom removed; and

FIG. 4 is a fragmentary side elevational view similar to FIG. 1 with the tool-carrying frame in a position approximately midway between its forwardmost and rearwardmost position relative to the support beam and with the near gusset plate of the tool-carrying frame being broken away.

The plow illustrated in the drawings is one of a number of which will be mounted on a frame to provide a rnulti-bottom plow implement. Each plow bottom is carried by a support beam 10 which extends in a fore and aft direction and has an elongated horizontally disposed mounting flange or bracket 12 secured on a longitudinally centered portion of its upper edge. The rear portion 13 of the support beam 10 is widened in a vertical direction to form a generally triangular shaped gusset plate in the inverted position. The rear edge of the plate portion 13 is indicated at 14. The opposite sides of the plate portion 13 provide large vertically disposed bearing surfaces for a tool-carrying frame 16 swingably mounted thereon. A transversely extending rearwardly opening socket or notch '18 of substantial depth is formed in the rounded upper rear corner 20 of the rear plate portion 13 for receiving a latching roller 55 as will be fully described hereinafter. The upper side of the notch 18 joins the rounded rear corner 20 at a small radius 22. An elongated horizontally extending slot 24 is provided in the rear plate portion 13 of the support beam 10 at a location forwardly of the rearwardly opening notch 18. Preferably both the slot 24 and the notch 18 are generally horizontally aligned with the longitudinal axis of the forward portion of the support beam 10. However, the slot 24 and notch 18 may be canted in any non-vertical direction. The tool-carrying frame 16 includes a pair of left and right vertically disposed gusset plates 26 of irregular, generally triangular shape, which are laterally spaced apart so as to have face-to-face sliding and bearing engagement with opposite sides of the rear portion 13 of the support beam 10. The upper rear corners of the pair of the spaced plates 26 which sandwich the plate portion 13 therebetween are secured together by a standard fastener 28 having a spacer 30 (FIG. 2) mounted thereon between the plates 26. The upper end of a beam foot 31 is rigidly secured between the lower portions of the gusset plates 26 by standard fasteners 32 and 33 with the lower depending end of the beam foot 31 beingv inclined forwardly and being adapted to have a ground-working tool rigidly secured thereto. In the agricultural implement shown in FIG. 1, the ground-working tool comprises a plow bottom 35 having a plow point 36, which plow bottom 35 is rigidly attached to the lower end of the beam foot 31 in known manner by a series of standard fasteners 37.

The upper front corners of the pair of gusset plates 26 are interconnected by a pivot bolt or pin 38 which extends through the elongated slot 24 formed in the rear portion 13 of the support beam 10 and carries a roller 39 which is guided in the slot 24 for movement therein forwardly and rearwardly of the support beam 10. The tool-carrying frame 16 and the plow bottom 35 rigidly attached thereto are therefore mounted on the rear plate portion 13 of the support beam 10 for both longitudinal movement forwardly and rearwardly thereof and pivoting movement about the horizontally disposed transverse axis of the pivot bolt 38. It is noted that the pivot axis is spaced high above the plow bottom 35 whereby during rearward and upward pivoting movement of the toolcarrying frame 16 and the attached plow bottom 35 the plow point 36 swings through a relatively flat or shallow are. If, on the contrary, the plow bottom 35 were pivotally mounted between the lower portions of the pair of gusset plates 26 at a point corresponding to the location of the fastener 33, the plow point 36, during rearward and upward pivoting movement of the plow bottom 35, would swing through a substantially deeper arc. This would be objectionable because a plow bottom in field operation usually cannot swing downwardly very far into the ground because of the resistance offered by an obstruction in the ground and so in order to release and swing backwardly, it is necessary to bodily raise the whole implement with considerable forces thus being exerted on the plow point and the over-all structure.

A pair of vertically disposed and aligned flanges 42 extend laterally from opposite sides of the central portion of the support beam 10 forwardly of the elongated slot 24 formed therein. A pair of horizontally disposed spring rods 43 are slidably mounted in bores formed one in each of the flanges 42 and have eye-formations 44 at their rear ends secured over the opposite ends of the pivot bolt 38. A pair of springs 45 are provided about the forward ends of the pair of spring rods 43 with the springs 45 being compressed between the forwardly facing surfaces of the flanges 42 and washers 46 secured on the forward ends of the rods 43 by nuts 47. The springs 45 yieldably urge the pivot bolt roller 39 toward the forward end of the elongated slot 24 whereby the tool-carrying frame 16 and the plow bottom 35 rigidly attached thereto are normally retained in their forwardmost positions relative to the support beam 10.

The pivoted tool-carrying frame 16 is further characterized by a pair of identical arms or links 50 which are disposed one against the outer surface of each of the gusset plates 26 and which are pivotably mounted at their lower ends thereon by a shoulder bolt 52. The upper ends of the arms 50 are interconnected by a shoulder bolt. 53 which extends through a pair of aligned elongated slots 54 formed in the gusset plates 26 whereby to permit limited pivoting movement of the upper ends of the arms '50 relative to the gusset plates 26. A latching roller 55 is provided on the shoulder bolt 53 intermediate the gus set plates 26. A torsion spring 57 is disposed about the shoulder bolt 52 and has-one end 58 disposed in abutting in the appropriate one of the gusset plates 26 whereby to permit limited pivoting movement of the arms 50 relative to the gusset plates 26.

With the tool-carrying frame 16 in its operable position as shown in full line in FIG. 1 and urged and held in its forewardmost position relative to the support beam 10 by the springs 45, the roller 55 associated with the arms 50 is resiliently retained by the torsion spring 57 in the ,forward end of the rearwardly opening notch 18 whereby to interlock or latch the tool-carrying frame 16 to the support beam 10 and thus normally prevent pivoting movement of the tool-carrying frame relative to the sup port beam 10.

During normal operation when the plow is being pulled through the ground, the reaction of the soil against the plow bottom 35 tends to pivot the plow bottom 35 rearwardly and upwardly around the pin 38. Such pivoting beam 10 whereby to cushion and'reduce the impact forces on the plow bottom 35 with the shock load being absorbed by the springs 45, thus substantially reducing the likelihood of the plow bottom 35, and particularly the plow points 36 thereof, being damaged. Unless such yielding reaches the predetermined overload point, the release or trip mechanism will not be actuated to permit rearward and upward swinging movement of the tool-carrying frame 16 and the plow bottom 35. For instance, referring to FIG. 4, the tool-carrying frame 16 is shown in a position approximately midway between its forwardmost and rearwardmost positions relative to the support beam 10 and, as is clearly illustrated, the rear roller 55 is still su1ficiently engaged in the notch 18 to prevent upward pivoting movement of the tool-carrying frame 16 relative to the support beam 10.

However, when the plow bottom 35 engages a sufliciently V unyielding obstruction, the springs 45 will yield sufiiciently to permit the tool-carrying frame 16 to move longitudinally rearwardly relative to the support'beam 10 a distance 1 sufficient to release or disengage the interlock roller 55' from the notch 18 whereby the roller 55 can snap up around the radius 22 at the upper rear end of the notch 18 to permit rearward and upward pivoting movement of the plow bottom 35 and the tool-carrying frame 16 about the pivot bolt 38 so as to clear the obstruction.

It will be seen that the longitudinal position occupied by the tool-carrying frame 16 when the roller 55 is disengaged from the notch 18 and passes around the radius 22 is its rearwardmost position relative to the support beam 10. After tripping, the force exerted on the plow point 36 by the obstruction during continued forward movement of the support beam 10 serves to swing the plow bottom 35 rearwardly and upwardly. The uppermost position of the plow bottom 35 is shown in broken line in FIG. 1, in which position the upper edges of the gusset plates 26 abut against the rear edge of the horizontal flange 12. As soon as the roller 55 passes over the radius 22 and the plow bottom 35 begins to swing clear of the obstruction, the springs 45 become operable to resiliently shift the tool-carrying frame 16 into its forwardmost position relative to the support beam with this action producing a loud enough noise as the roller 39 strikes the front end of the slot 24 to let the tractor operator know that the plow bottom 35 has been released and is in its non-working position.

To reset the plow bottom 35 in its operable position, the tractor operator has only to back up a few feet or raise the implement so that the plow bottom 35 can swing down freely. When the plow bottom 35 swings downwardly into its operable position, the rear roller 55 rides downwardly over the rounded corner 20 of the rear plate portion 13 of the support beam 10 until it snaps into the notch 18. Since only the relatively light torsion spring 57 has to be compressed to let the rear roller 55 enter the notch 18, the forces to reset the plow bottom 35 in its operable position are relatively small.

The plow bottom 35 may be manually released for rearward and upward movement, as, for instance, to more conveniently position it for replacing the plow points 36, etc., manual release is effected by merely swinging the arms 50 rearwardly against the force of the torsion spring 57 until the rear roller 55 is disengaged from the notch 18. The plow can now be lifted freely.

When the plow bottom 35 or other tool is in its working position, and for the initial portion of its tripping or release movement the gusset plates 26 have full to nearly full bearing support engagement with the bearing surfaces of the wide beam rear portion 13. Thus, even though the tool is mounted for both cushioned and at times pivoting movement it has adequate bearing support at all times.

It will be understood that certain changes may be made in the construction of arrangement of the spring cushioning and release mechanism for a ground-working tool disclosed therein without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. In a ground working implement, in combination, a fore and aft support beam, a tool-carrying frame having a ground-working tool attached thereto and depending therefrom, said beam having a non-vertical elongated slot formed therein, a guide roller operable in said slot between forwardmost and rearwardmost positions therein, means mounting an upper front corner of said tool-carrying frame on said guide roller whereby said tool-carrying frame is mounted on said support beam for both pivoting movement about a horizontal transverse axis and fore and aft shifting movement with respect thereto, a rearwardly opening notch of substantial depth formed in the rear edge of said support beam, a latching roller, means for supporting said latching roller on the upper rear corner of said tool-carrying frame for engagement in said notch when said tool-carrying frame is disposed forwardly of its rearwardmost position relative to said support frame wlhereby to latch said tool-carrying frame against pivoting movement relative to said support beam, said latching roller being disengageable from said notch upon rearward shifting movement of said tool-carrying frame into its rearwardmost operating position relative to said support beam whereby to permit rearward and upward pivoting movement of said tool-carrying frame relative to said support beam, and yieldable means interconnecting said support beam and said tool carrying frame for yieldably retaining said frame in its forwardmost position relative to said support beam.

2. In a ground-Working implement, in combination, a fore and aft extending support beam, a tool-carrying frame having a ground-working tool attached thereto and depending therefrom, roller and elongated slot means interconnecting the upper front corner of said tool-carrying frame on said support beam for pivoting movement relative thereto about a horizontal axis transverse to said beam and for longitudinal shifting movement forwardly and rearwardly thereof, said axis for pivoting movement being spaced adjacent the top of said support beam whereby the point of said tool swings through a relatively flat shallow are when said tool-carrying frame and tool are pivoted rearwardly and upwardly relative to said support beam, a rearwardly opening notch of substantial depth formed in the rear edge of said support beam, arm means pivotally mounted on said tool-carrying frame adjacent the rear edge thereof and below said notch for limited pivoting movement relative thereto and having a latching roller mounted on the upper end thereof, means resiliently urging said arm means in a forward direction whereby to seat said latching roller in said notch when said toolcarrying frame is disposed forwardly of its rearwardmost position relative to said support frame whereby to prevent pivoting movement of said tool-carrying frame relative to said support frame, said latching roller being automatically disengaged from said notch upon longitudinal movement of said tool-carrying frame into its rearwardmost operative position relative to said support beam, and spring means mounted on said support beam and operably connected to the upper front corner of said toolcarrying frame for normally urging said frame into its forwardmost position relative to said support beam, said spring means being yieldable upon engagement of said ground-working tool with an unyieldable obstruction with said tool-carrying frame being thereupon longitudinally shifted into its rearwardmost position to disengage said latching roller from said notch and permit rearward and upward pivoting movement of said tool-carrying frame and said tool relative to said support beam to clear the obstruction.

3. In a ground-working implement, in combination, a fore and aft extending support beam, a tool-carrying frame having a ground-working tool attached thereto and depending therefrom, said tool-carrying frame comprising a pair of parallel spaced apart plate members, an elongated non-vertical slot formed in said support beam, a guide roller movable in said slot forwardly and rearwardly of the support beam, a pivot bolt interconnecting the upper front corner of said tool-carrying frame and supporting said guide roller for mounting said tool-carrying frame on said support beam for both longitudinal shifting movement forwardly and rearwardly thereof and pivoting movement relative thereto, said plate members of said tool-carrying frame being disposed on opposite sides of said support beam which is sandwiched therebetween, a rearwardly opening notch of substantial depth formed in the rear edge of said support beam and a latching roller mounted on the rear portion of said tool-carrying frame for latching engagement in said notch when said tool-carrying frame is disposed forwardly of its rearwardmost position relative to said support frame whereby to prevent pivoting movement of said tool-carrying frame relative to said support beam, and spring means mounted on said support beam and operably connected to said upper front corner of said tool-carrying frame for yieldably urging said tool-carrying frame into its forwardmost position, said latching roller being automatically released from said notch upon longitudinal movement of said toolcarrying frame into its rearwardmost operative position relative to said support beam as upon non-yielding engagement of said ground-working tool with an obstruction whereby to permit rearward and upward pivoting movement of said tool-carrying frame relative to said support beam.

4. In a ground-working implement, in combination, a fore and aft extending support beam, a tool-carrying frame having a ground-working tool attached thereto and depending therefrom, said tool-carrying frame comprising a pair of vertically disposed spaced plate members, an

elongated generally horizontally extending slot formed in said support beam, a guide roller disposed in said slot for movement forwardly and rearwardly therein, a pivot bolt interconnecting the upper front corner of said toolcarrying frame and providing an axle for said roller thereby mounting said tool-carrying frame on said support beam for longitudinal movement forwardly and rearwardly thereof and for pivoting movement relative thereto about the axis of said bolt, said plate members of said toolcarrying frame being disposed one on each side of said support beam in both sliding and pivoting bearing engagement therewith, a rearwardly opening notch of substantial depth formed in the rear end of said support beam in generally horizontal alignment with said elongated slot, a latching roller pivotally mounted on the rear portion of said tool-carrying frame and resiliently urged forwardly into latching engagement in said notch when said toolcarrying frame is disposed forwardly of its rcarwardmost tripping position relative to said support beam whereby to latch said tool-carrying frame with said support beam and prevent relative pivoting movement therebetween, said latching roller being automatically released from said notch upon longitudinal movement of said tool-carrying frame into its rearwardmost position relative to said support beam, and spring means operably connected between said support beam and the upper front corner of said toolcarrying frame for resiliently retaining said tool-carrying frame in its forwardmost position relative to said support beam, said spring means being yieldable upon engagement of said ground-working tool with an unyielding obstruc tion to permit shifting of said tool-carrying frame into its rearwardmost position whereby to release said latching roller from said notch and permit rearward and upward pivoting movement of said tool-carrying frame relative to said support beam to clear the obstruction.

5. In a ground working implement, in combination, a fore and aft extending traveling support beam, 9. toolcarrying frame including a pair of vertically disposed laterally spaced interconnected plate members disposed one on either side of a rear portion of said support beam so as to sandwich said rear portion therebetween, said tool-carrying frame having a ground-working tool attached thereto and depending therefrom, an elongated approximately horizontally extending slot formed in said rear portion of said support beam, a guide roller disposed in said slot for movement therein forwardly and rearwardly of said support beam, a pivot bolt interconnecting the upper front corner of said tool-carrying frame and forming an axle for said guide roller thereby mounting said frame on said support beam for longitudinal movement forwardly and rearwardly thereof and for pivoting movement relative thereto on said pivot bolt, said pivot bolt being spaced a substantial distance above said ground-working tool whereby the point of said tool swings through a relatively flat shallow are upon upward ,and rearward pivoting movement of said toolcarrying frame and said tool relative to said support beam, a transversely extending rearwardly opening notch of substantial depth formed in the rear end of said support beam in generally horizontal alignment with said elongated slot, a pair of arms pivotally mounted at their lower ends on a rear portion of said tool-carrying frame and having a latching roller mounted between their upper ends and adapted for latching engagement in said notch, first spring means operably connected between said tool-carrying frame and said pair of arms for urging same in a forward direction whereby to resiliently retain said latching roller in said notch when said toolcarrying frame is disposed forwardly of its rearward most position relative to said support beam whereby to latch said tool-carrying frame with said support beam and prevent relative pivoting movement therebetween, and second spring means operably connected between said support beam and the upper front corner of said tool-carrying frame for yieldably retaining said toolcarrying frame in its forwardmost position relative to said support beam, said second roller being automatically disengaged from said notch upon longitudinal movement of said tool-carrying frame into its rearwardmost position relative to said support beam as upon engagement of said ground-working tool with an unyielding obstruction whereby to permit upward and rearward pivoting movement of said tool-carrying frame and tool relative to said support beam to clear the obstruction.

6. In a ground working implement of the character described, in combination, a fore and aft support beam the rear portion of which is in the form of a vertical gusset bea-ring plate, a tool-carrying frame having a ground working tool attached thereto and depending therefrom,

said frame comprising a pair of interconnected gusset plates spaced apart in parallel relationship so as to sand wich said vertical gusset bearing plate therebetween so as to receive continuous bearing support engagement therefrom, and means for pivotally mounting said frame on said vertical gusset bearing plate on a horizontal axis passing through upper and forward portions of said vertical gusset bearing plate and of said frame.

7. In a ground working implement of the character described, in combination, a fore and aft support beam the rear portion of which is in the form of a generally triangular shaped vertical gusset plate with the base thereof being ontop and the point at the bottom, a toolcarrying frame having a ground working tool attached thereto and depending therefrom, said frame comprising a pair of generally triangular shaped interconnected gusset plates spaced apart in parallel relationship so as to sandwich said vertical gusset bearing plate therebetween so as to receive continuous bearing support engagement therefrom, means for pivotally connecting the front upper corner of said interconnected gusset plates with the front upper corner of said vertical gusset bearing plate, and latch means latching the rear upper corner of said interconnected gusset plates to the rear upper corner of said vertical gusset bearing plate.

8. The combination called for in claim 7 wherein said latch means is provided by a latching roller mounted on said interconnected gusset plates which normally is seated within a notch formed in the rear edge of said vertical gusset bearing plate and the rear upper corner of the latch is rounded above said notch to provide a cam surface forsaid roller when said latch means is tripped and said tool and tool-carrying frame swing rearwardly and upwardly.

References Cited by the Examiner UNITED STATES PATENTS 1,078,871 11/1913 Olso-n 172 -269 2,707,425 5/1955 Charley 172269 2,913,059 11/1959 Toland etal 172-269X FOREIGN PATENTS 161,484 11/1957 Sweden.

ABRAHAM G. STONE, Primary Examiner.

CARL W. ROBINSON, ANTONIO F. GUIDA,

Examiners. J. R. OAKS, Assistant Examiner. 

1. IN A GROUND WORKING IMPLEMENT, IN COMBINATION, A FORE AND AFT SUPPORT BEAM, A TOOL-CARRYING FRAME HAVING A GROUND-WORKING TOOL ATTACHED THERETO AND DEPENDING THEREFROM, SAID BEAM HAVING A NON-VERTICAL ELONGATED SLOT FORMED THEREIN, A GUIDE ROLLER OPERABLE IN SAID SLOT BETWEEN FORWARDMOST AND REARWARDMOST POSITIONS THEREIN, MEANS MOUNTING AN UPPER FRONT CORNER OF SAID TOOL-CARRYING FRAME ON SAID GUIDE ROLLER WHEREBY SAID TOOL-CARRYING FRAME IS MOUNTED ON SAID SUPPORT BEAM FOR BOTH PIVOTING MOVEMENT ABOUT A HORIZONTAL TRANSVERSE AXIS AND FORE AND AFT SHIFTING MOVEMENT WITH RESPECT THERETO, A REARWARDLY OPENING NOTCH OF SUBSTANTIAL DEPTH FORMED IN THE REAR EDGE OF SAID SUPPORT BEAM, A LATCHING ROLLER, MEANS FOR SUPPORTING SAID LATCHING ROLLER ON THE UPPER REAR CORNER OF SAID TOOL-CARRYING FRAME FOR ENGAGEMENT IN SAID NOTCH WHEN SAID TOOL-CARRYING FRAME IS DISPOSED FORWARDLY OF ITS REARWARDMOST POSITION RELATIVE TO SAID SUPPORT FRAME WHEREBY TO LATCH SAID TOOL-CARRYING FRAME AGAINST PIVOTING MOVEMENT RELATIVE TO SAID SUPPORT BEAM, SAID LATCHING ROLLER BEIND DISENGAGEABLE FROM SAID NOTCH UPON REARWARD SHIFTING MOVEMENT OF SAID TOOL-CARRYING FRAME INTO ITS REARWARDMOST OPERATING POSITION RELATIVE TO SAID SUPPORT BEAM WHEREBY TO PERMIT REARWARD AND UPWARD PIVOTING MOVEMENT OF SAID TOOL-CARRYING FRAME RELATIVE TO SAID SUPPORT BEAM, AND YIELDABLE MEANS INTERCONNECTING SAID SUPPORT BEAM AND SAID TOOL CARRYING FRAME FOR YIELDABLY RETAINING SAID FRAME IN ITS FORWARDMOST POSITION RELATIVE TO SAID SUPPORT BEAM. 